Protease Treatment for the Stabilization of Rice Bran: Effects on Lipase Activity, Antioxidants, and Lipid Stability

Abstract

Cereal Chem. 91(6):560-565Rice bran lipid is rapidly made rancid by endogenous lipase enzymes. To inactivate rice bran lipase, an enzymatic hydrolytic method was developed and then compared with the thermal method. The efficiency of five proteolytic enzymes including trypsin, chymotrypsin, papain, bromelain, and Flavourzyme enzyme to stabilize rice bran was investigated. Moreover, the antioxidant content and storage stability of enzymatically stabilized rice bran (ESRB), thermally stabilized rice bran (TSRB), and raw rice bran (RRB) were studied. Trypsin, chymotrypsin, and papain showed a higher rate of hydrolysis than bromelain and Flavourzyme enzyme. After 120 min of hydrolysis, rice bran hydrolyzed by trypsin, chymotrypsin, and papain inactivated 80, 86, and 79% of lipase activity, respectively, whereas lipase activity of rice bran hydrolyzed by bromelain and Flavourzyme enzyme was higher than the initial rice bran. With a similar lipase inactivation level, the cheaper papain was used to produce ESRB. Total phenolics content of ESRB was 52.89 and 94.10% higher than in RRB and TSRB, respectively. In addition, γ-oryzanol content in ESRB was 2.23-and 2.05-fold of that in RRB and TSRB, respectively. Lipase activity of RRB increased throughout the two months of storage, whereas no change in lipase activity was observed in ESRB and TSRB. At the end of storage, free fatty acid contents of RRB, TSRB, and ESRB were 15.30, 4.67, and 3.92%, respectively. We propose enzymatic hydrolysis by papain for stabilization of rice bran with high antioxidant content and storage stability.

Comparative Evaluation of the Nutritional, Antinutritional, Functional, and Bioactivity Attributes of Rice Bran Stabilized by Different Heat Treatments

“…According to the results presented in Table 4 , the contents of tocotrienols and tocopherols in heat-treated RB were significantly lower than the untreated material ( p < 0.05), which was presumably due to the degradation of the heat-sensitive antioxidants, with a loss of 15.8 and 20.5% for tocopherols and tocotrienols, respectively. On the contrary, γ-oryzanol was not reduced significantly ( p < 0.05) by all heat treatments, as it has been reported to be a relatively thermostable antioxidant [ 63 ]. Untreated RB had the highest γ-oryzanol content, whereas the microwave-heated RB the lowest concentration among all the heat-treated RB samples.…”

The anti-cancer activity and potential clinical application of rice bran extracts and fermentation products

“…3,4 The protein content comprises approximately 10-15% of rice bran, and it is increased to 18% in defatted rice bran. 5 The protein content includes albumin (water soluble), globulin (salt soluble), prolamin (alcohol soluble), and glutelin (alkali soluble). 6 The rice bran protein contains all the essential amino acids.…”

Comparison of 11 rice bran stabilization methods by analyzing lipase activities

“…In comparison with pepsin, papain held a better inactivation effect of 80.48% remained after 90 min treatment. Protease like pepsin and papain were reported to be used in rice bran stabilization (Laokuldilok & Rattanathanan, ). But owing to the high price of protease and less efficacy, using protease for rice bran stabilization is not a wise choice.…”

“…The fundamental reason of high-free fatty acid content in rice bran is the rice bran lipase, so inactivating rice bran lipase is a commonly used method for rice bran stabilization (Ju & Vali, 2005). Up to now, many methods of stabilizing rice bran have been reported, such as chemical stabilization or refrigeration (Amarasinghe et al, 2009), parboiling or hydrothermal treatment (María et al, 2016;Pradeep, Jayadeep, Guha, & Singh, 2014), extrusion (Kim, Byun, Cheigh, & Kwon, 2010), microwave treatment (Nordin, Karim, Ghazali, Adzahan, & Sultan, 2014;Patil et al, 2016), infrared radiations (Wang, Khir, et al, 2017), ohmic heating (Dhingra, Chopra, & Rai, 2012), steam heating (Thanonkaew, Wongyai, Mcclements, & Decker, 2012), and biological enzyme method like papain or other enzymes (Laokuldilok & Rattanathanan, 2014). Although these rice bran stabilization methods have been reported, the utilization rate of rice bran is still extremely low; that is, because the major rice processing factories in developing countries are lack of stabilization equipment or too high energy and equipment cost lead to the low utilization rate.…”